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Target 3: Rhea and Tethys

Target 3: Rhea and Thetys

Cassini Research Scientist

Hi everyone. My name is Morgan.
I'm a research scientist for the Cassini mission.

My job is to help Cassini scientists and engineers work together to achieve amazing discoveries.

My favorite target is Target 3, because this set of images will show something very special called an ‘occultation.’
Occultations happen when one object, like a planet or a moon, passes in front of another, hiding it from view.
In this case, Rhea will pass in front of Tethys.
Occultations like this give us a very accurate way to assess the orbits of these moons,
which change slowly over time.

I like Rhea and Tethys because they are still mysteries to us in some ways.
We aren't sure what the interior of Rhea looks like.
Some of our measurements suggest it has a rocky core,
but other data indicates it is the same throughout.
Tethys is also intriguing.
It's composed almost entirely of water-ice,
which makes it one of the whitest and brightest objects in the solar system.

Recently some reddish streaks, termed “tiger scratches” have been seen that don't match with any surface features.
Their origin is currently a mystery, which is why I hope you select Target 3.
Good luck with your decision, and have fun!